The present invention relates to a technology for measuring an intake air flow amount in an internal combustion engine provided with a variable valve mechanism that varies a valve operating characteristic of an intake valve.
Heretofore, there has been known a variable valve mechanism having a configuration of varying continuously valve lift amounts of exhaust/intake valves (refer to Japanese Unexamined Patent Publication No. 2001-012262).
Meanwhile, there has been proposed a control of intake air amount by varying a valve operating characteristic of an intake valve by such a variable valve mechanism.
In this intake air amount control, since it is possible to control an intake air amount by an intake valve just before a cylinder, a control excellent in a transient response characteristic can be performed. However, in order to control a fuel injection quantity without a delay for the intake air amount, it is required to measure with high accuracy an intake air flow amount in a cylinder portion.
The present invention has been accomplished in view of the above problem, and has an object to measure an intake air flow amount with high accuracy in an intake air amount control mainly by an intake valve.
In order to achieve the above object, the present invention is constituted to measure, in the following manner, an intake air flow amount of an internal combustion engine provided with a variable valve mechanism that varies a valve operating characteristic of an intake valve.
Firstly, a valve operating characteristic of the intake valve is detected. Then, a flow loss coefficient and an effective opening area of the intake valve are calculated based on the valve operating characteristic. Thereafter, an intake air flow amount in a cylinder portion is calculated based on parameters inclusive of the calculated flow loss coefficient and effective opening area.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.